1. Field of the Invention
The present invention relates to an ammonia still apparatus and method for purifying ammonia from contaminated refrigeration fluid.
2. Description of the Related Art
In the classic compression type refrigeration system, a refrigerant is alternately compressed and expanded. In a simple closed loop compression type refrigeration system, there is at least a compressor, an evaporator, a throttling or metering device, and a condenser. During one stage of the compression type refrigeration cycle, a low pressure refrigerant vapor enters the compressor. At this point in the cycle, work is required of the compressor in. order to raise the pressure and the boiling point of the refrigerant vapor. In the next phase of the compression type refrigeration cycle, the high pressure, high temperature refrigerant vapor leaving the compressor is transferred through a heat exchanger called a condenser. A second fluid passes through the condenser in order to remove heat from the refrigerant vapor, thereby transforming the refrigerant vapor to a refrigerant liquid. As the refrigerant liquid exits the condenser, it leaves at the same pressure but at a lower temperature than it had upon entering the condenser.
Next, the refrigerant passes through a throttling device that reduces the pressure, temperature and boiling point of the fluid. In the last step of the typical compression type refrigeration cycle, refrigerant travels through an evaporator to receive heat from some other fluid in communication with the evaporator to achieve the desired cooling effect of this other fluid. Such a closed loop compression refrigeration cycle is duplicated in order to repetitively remove heat from a body of fluid in communication with the evaporator.
Commercial and industrial refrigeration systems typically use anhydrous ammonia. Anhydrous ammonia is the liquid form of pure ammonia gas and is technically water-free. Most refrigeration experts consider industrial grade anhydrous ammonia to be the most economical and efficient heat transfer medium for industrial refrigeration processes.
Water, unfortunately, finds its way into the refrigeration system, and over time, accumulates to a level of concern. Ammonia readily associates with water to form ammonium hydroxide, an inferior refrigerant that reduces the efficiency of the refrigeration system. The reduced efficiency increases the use of energy consumed in the system, thus increasing the cost of operation and also accelerates wear and tear on equipment causing shorter mean time to failure.
In an industrial refrigeration system, compressors, piping, and vessels containing anhydrous ammonia are prevalent throughout the refrigeration plant. Such a refrigeration system generally has lubricating oils inserted into the compressor for lubrication. Invariably, some of the oil or other lubricant migrates throughout the system, mixing with the anhydrous ammonia. Since the oil serves as an insulator or retardant to heat transfer, a high prevalence of waste oil in a refrigeration system compromises the efficiency of the refrigeration process. In addition, chemical reactions can occur between the oil, ammonia and/or water to produce additional waste products, such as sludge and acids. The addition of oil and water to ammonia can also provide a rich medium for microbiological growth which can produce slime and acids to further degrade the efficiency of operation as well as physically damage the system.
In order to prevent deterioration of the refrigeration efficiency as well as the physical parts of the system, accumulations of waste lubricating oil and water need to be purged from the system. Most commercial and industrial refrigeration units include one or more ports located at a lower level in the piping system and arranged such that lubricating oil will accumulate there to be drained from the pipes for collection and/or discarding. Unfortunately, the ammonia is wasted in these systems.
Therefore a need exists to purify and recycle ammonia in a refrigeration system from waste fluid having waste oil and water contaminants while preventing the undesirable side effects associated with draining waste fluid.